Here,
#cost=-7/19=> color(blue)(II^(nd)Quadrant
)orIII^(rd)Quadrant...to(1)#
#tant < 0=> color(blue)(II^(nd) Quadrant) or
IV^(th)Quadrant...to(2)#
From #(1) and (2)#,we can say that
#pi/2<= t <= pi to color(blue)(II^(nd) Quadrant)=>(sine) > 0 #
So,
#(i).sin(t)=+sqrt(1-cos^2t)=sqrt(1-49/361)=sqrt312/19=
(2sqrt78)/19#
We know that,
#"cosine is "color(red)"even function"=>cos(-theta)=costheta#
#(ii).cos(-t)=cost=-7/19#
Note:
#pi/2<= t <= pi =>-pi/2 >= (-t) >= -pi#
#i.e.-pi <= (-t) <= -pi/2=>III^(rd) Quadrant=># cosine #< 0#